Spa$al and temporal heterogeneity
of the comprehensive fer$lity of soils
under oil palm a7er EFB applica$on
Authors:
Marc-‐Philippe CARRON
1, Quen7n AURIAC
1, Mélodie PIERRAT
1, Didier SNOECK
1, SUHARDI
2, Raphaël MARICHAL
1, Jean-‐Pierre CALIMAN
1, 2Context:
The empty fruit bunches (EFB), a mill by-product resulting from the extraction of palm oil, can be recycled in the palm plantations in partial substitution of mineralmanures. How to manage organic residues and mineral fertilizers regarding the comprehensive fertility (physical, chemical and biological) of soil? Our research project addressed the impact of these organic inputs on soil biota and associated physical and chemical parameters. The goal is to use the comprehensive soil fertility as a tool in ecological intensification. The current study relates the characterization of both spatial and temporal heterogeneity within the plots.
Temporal Study
Materials and Methods
- The temporal heterogeneity of the soil characteristics under EFB applied on harvest pathway (P zone) was assessed on plots receiving EFB every two years. The control was P zone in Conv without EFB application.
- A time-sequence with six points was built, taking into account the length of time after the application of EFB; i.e. after: 1, 3, 6, 12, 18, and 24 months (Figure 1). - Soil samples were analysed for:
• Chemical & physical parameters, • Macrofauna,
• Nematofauna.
Spatial study
Materials and Methods
Five zones around the palm were determined based on the heterogeneity of the habitat around the tree, and the spatial heterogeneity of chemical and organic fertilizers applications (Figure 2).
Two practices were studied: • “EFB”(60 t/ha every two years) • “Conv” without EFB as control.
Soil samples were taken three months after EFB application on P zone. Samples were analysed for:
• Chemical & physical parameters, • Macrofauna,
• Nematofauna, • Microorganisms.
Results
The evolution of chemical and biological parameters led to identify three periods:
• The first period (first 6 months following the EFB application) was characterised by a strong
disturbance of all soil parameters. Particularly, it
resulted in a significant increase in pH, K, base saturation and macrofauna abundance, mostly the ants. In the same time, we observed a strong reduction of the earthworm and nematode populations.
• The intermediate period (between 12th and 18th month
after EFB application) looked like a resilience time.
• The last period (starting from the 24th month) was
marked by the maximum improvement of most of the
fertility parameters: bulk density, CEC, N, Ca, C and clay. It was also characterized by a maximum abundance in earthworms, earwigs (Dermaptera), and millipedes (Diplopods).
• The nematofauna was more abundant over the two last periods and more balanced on the functional level, testifying the effectiveness of the resilience
.
Results
A formula was developed to calculate the mean value of the plot:
Plot mean = ∑(S
i× D
i)
; where Si = (area of zone i) / (total area of plot), and Di = data of zone i (where i = P, PC, C, CW, W).For the EFB practice, chemical richness was more important on P and C zones than on W zone. Also, the macrofauna was more abundant on PC and C zones than on W zone (Table 1).
When comparing both practices (“Conv.” and “EFB”), the EFB application was correlated with significant increase of chemical and biological parameters on P and PC. The impact extended significantly to C and W zones for some characteristics (Table 1).
On the PCA, earthworms showed a different pattern than other macrofauna taxa
(Figure 3a). In Conv., PC/Conv. and P/Conv. had similar characteristics, but different from C/Conv. and CW/Conv. that are also different from W/Conv.. While in EFB plots, PC/EFB showed a different pattern than all other zones, not different between them
(Figure 3b).
Nematofauna density was low in most studied areas (3 ind.g-1 of soil), except for
the C zone in Conv (8 ind.g-1 of soil).
Microorganism DNA density was lower in EFB plot than in Conv, particularly for C and W zones.
Based on these results, we can suggest to consider three zones in Conv. (P+PC, C +CW, and W) and four zones when EFB is applied along the pathway (P, PC, C+CW, and W) for further studies.
Figure 2: Five Soil sampling zones: P: Pathway, PC: transition zone between P and C, C: Circle,
CW: transition zone between C and W, W: Windrow.
Study site:
Trial sites: Libo Estate, Riau/Sumatra – IndonesiaTable 2: Changes in organic soil layer (0 to 3.5 cm) on P zone for the three periods after EFB application, compared to P zone in Conv
Soil parameters 1 to 6
months 12 to 18 months 24 months Bulk density + ++ +++ C organic + + ++ pH +++ + N tot + + ++ K +++ + + CEC ++ + +++ Ca + ++ ++ Saturation +++ ++ +
Organic cover (biomass) +++ ++ +
Macrofauna density +++ + ++ ● Earthworms -‐ ++ +++ ● Ants +++ + + ● Coleoptera +++ ++ ● Diplopodes -‐ -‐ -‐ + +++ ● Dermaptera + + +++ Nematofauna density ++ ++ ● N bacterivorous + ++ ● Maturity Index (MI) -‐
● Index for breaking down (NCR) +
Addresses:
1 Cirad, UR Systèmes de Pérennes,
Agropolis Avenue, 34398 Montpellier cedex 5 (France)
2 Smart-RI, Po Box 1340, 28000
Pekanbaru, Riau (Indonesia)
Figure 3: PCA of community structure
(a) Variables: soil macrofauna taxa. (b) Ordination of
sampling zones in the plane defined by the first two axes. Labels correspond to the barycentres of zone/treatment. (Monte Carlo test, p < 0.01, Observation = 0.42)
Figure 1: Six sampling times after EFB application
1 month 3 months 6 months 12 months 18 months 24 months
Conclusion & Perspectives
§ Sampling and analysis methods, adapted to this type of cropping system having complex spatio-temporal heterogeneity, are proposed
§ Our results show that EFB can improve the comprehensive soil fertility and reduce spatial heterogeneity in the plot. Particularly, the application of EFB induce strong disturbance of soil characteristics during first 6 months; but then, all characteristics gradually improve, except K. After 24 months. fertility of P/EFB is still significantly higher than P/Conv.
§ Our work provide first methods and data towards a holistic approach of the soil fertility under mature oil palm.
§ They bring new highlight on the impacts of organic application in space and time. They raise new questions on how to manage inorganic and organic fertilization practices (types, doses and frequencies) regarding the comprehensive soil fertility.
Table 1: Comparison of the evolution of chemical
and biological characteristics around a palm with or without EFB application
+ higher value, - lower value, compared to W/EFB used as reference
The soil parameter was improved , decreased , compared to the same zone in Conv
P PC C CW W
P PC C CW W
pH +++ ß ++ +++ P + ++ ß + K +++ + ++ ß -‐ -‐ + CEC -‐ + ß -‐ -‐ + -‐ Ca + -‐ ß + Mg + + ++ ß + + Saturation +++ ++ ++ ß-‐-‐-‐ -‐-‐-‐ -‐ -‐ Organic cover (biomass) -‐-‐ -‐ -‐ ß
-‐-‐ -‐ -‐ Macrofauna (biomass) -‐ + + ß
-‐-‐ -‐ -‐ -‐ Macrofauna (Density) -‐ -‐ -‐ ß
-‐-‐ -‐ ++ -‐ -‐ Earthworms (Density) -‐-‐ ++ -‐ -‐ ß
-‐-‐-‐ -‐ -‐ -‐ Ants (Density) -‐-‐ -‐-‐-‐ -‐ ß
-‐-‐-‐ -‐-‐-‐ -‐ Dermaptera (Density) -‐-‐-‐ -‐-‐-‐ ß
